88. Role of fumonisins as effectors in the complex interplay between maize and Fusarium verticillioides

ARIAS, SL; THEUMER, MG; RUBINSTEIN, HR

Mendoza

Congreso; Strategies to reduce the impact of mycotoxins in Latin America in a global context; 2011

International Society for Mycotoxicology (ISM) and The Latin American Society for Mycotoxicology (SLAM).

Fusarium verticillioides is best known for its worldwide occurrence on maize and the associated concern with fumonisins production. The infection of maize by the fungus can result in highly variable disease symptoms ranging from asymptomatic plants to severe rotting and wilting. This study focuses on understanding the role of fumonisins as effectors and the impact on the outcome of the disease interaction in resistant and susceptible hybrids. Resistant (RH, LT 622 MG) and susceptible (SH, HX 31P77) maize hybrids (Presello, 2009) were planted in pots containing autoclaved sand (10 seeds by treatment) and watered with solutions of FB1 (0, 1 and 20 µg/ml) on days 2, 4, and 6 after planting (dap), and with sterile water until harvests (days 7, 14 and 21). Fumonisins were prepared by culturing F. verticillioides (2024 strain, UNRC) in Myro liquid medium in bioreactor. FB1: FB2: FB3 ratio in the fermented medium was 88:5:7, obtained by HPLC. Disease symptoms and growth parameters were evaluated by visual inspection and by digital analysis of root picture (Root Image Analyzer software), respectively. The specific root length (SRL) and leaf dry matter content (LDMC) indices were calculated as the ratios of total root length: root dry mass and leaf dry mass: fresh mass, respectively. Visual symptoms of disease included stunting, wilting, mild bleaching; leaf- rolling and necrotic leaf and root lesions were evident as early as 7 days and persisted for at least 21 (dap), in RH and SH watering with 20 µg/ml of FB1. Moreover, the phytotoxic effects were exhibited in the seedling growth and development. The overall trend was suppression of the plant height; primary root length, aerial part and root weight and total biomass on day 7 and continued on day 21 for RH and SH in plant watering with 1 and 20 µg/ml of FB1. However, adaptive response to the least FB1 concentration was seen at 21 days in both hybrids. Interestingly, the SRL were altered in RH only when the highest FB1 concentration was tested. Even through, SH treatment with 1 and 20 µg/ml of FB1 showed significantly lower SRL than their controls. LDMC indices were higher in RH and SH watered with the highest FB1 concentration at 7, 14 and 21 days. These results show that the fumonisins themselves were able to cause the symptoms similar to those seen in F. verticillioides maize seedling disease. Furthermore, fumonisins affected negatively root elongation and relative growth rates and nutrient and water uptake capacities in all of the treatment groups except in the RH watering with 1 µg/ml of FB1 that were reflect in the SRL parameter. On other hand, the fumonisins could be altered the levels of membrane permeability due to water regulation of leaves correlated with a lower LDMC indices described. Comprehensive knowledge of function of pathogen effectors and the perturbations they cause in plants is a precondition for understanding the basis of pathogenesis and disease.